Vacuum blood collection systems are well known in the art and have been utilized for a number of years. The basic patent for this type of system is U.S. Pat. No. 2,460,641. The conventional system employs a double ended needle with a hub intermediate its ends which is adapted to be mounted to a holder so that one end of the needle extends forwardly of the holder and the rear end of the needle extends into an interior hollow chamber in the holder. The rear end of the holder is open to permit introduction of a stoppered evacuated tube into alignment with the rear end of the needle so that the needle can penetrate the stopper and communicate with the interior of the container. When the forward end of the cannula is introduced into a vein and the rear end of the cannula is introduced into an evacuated tube, the pressure differential between the venous pressure and the evacuated tube will cause blood to flow into the tube for collection of a blood sample. U.S. Pat. Nos. 3,965,889; 3,890,955 and 3,817,240 are examples of this conventional system.
Throughout the years various improvements have been made to the collection system such as by providing various types of valves to shut-off flow from the vein while evacuated tubes are interchanged for purposes of collecting a multiplicity of samples. Examples of this type of arrangement are present in U.S. Pat. Nos. 3,494,352 and 3,469,572.
Further improvements in the basic system have employed various types of blood tell tales to indicate correct positioning of the device in the vein. Examples of this type of structure are depicted in U.S. Pat. Nos. 3,942,514; 3,886,930 and 3,817,240.
Another improvement in the basic structure includes the provision of indexing means on the holder and stoppered tube for purposes of indicating the relative position of the stopper and the cannula. U.S. Pat. No. 3,366,103 is representative of this stage of development in the art.
The number of blood samples being collected for testing and analysis is ever increasing and the need for more improved sampling systems of a simple and disposable nature for mass use is ever present.